Calibrated conduit caliper and method

A well casing caliper calibrating apparatus comprising:

• A. A well casing analog tube having a slot defined in its wall to receive one feeler arm of a plurality of feeler arms of an elongated caliper tool axially centralized within said tube;
• and
• B. Positioning means operative with said tube variously:
• (1) To position said one feeler arm into position representative of a casing wall thickness in a well casing;
• (2) To position said one feeler arm into position representative of the nominal internal diameter of said well casing;
• and
• (3) To position said one feeler arm into position representative of a designated minimum space through said well casing.

A method of calibrating a well casing caliper tool at the earth's surface, said caliper having a plurality of feeler arms, comprising the calibrating steps of:

• A. Coaxially centralizing said tool within a casing analog tube to equally confine said feeler arms;
• B. Calibrating an indication from said tool while causing one arm of said feeler arms to be in position representing a designated wall thickness of a well casing;
• C. Calibrating another indication from said tool while causing said one arm to be in position representing the nominal internal diameter of said well casing:
• and
• D. Calibrating a third indication from said tool while causing said one arm to be in position representing a designated minimum space through said well casing;
• E. Said calibrating steps being performed in any sequence.

In an internal diameter caliper having a tool body provided to be coaxially aligned within a generally cylindrical conduit, a plurality of feeler arms with each said feeler arm mounted through bearing means with said body and provided to be urged by respective first resilient biasing means to radially extended positions relative to the axis of said tool, a first linear motion transfer means adapted for forceful contact with that first feeler arm having the greatest radial extension of any said feeler arm and adapted for linear movement corresponding to the extension of said first feeler arm, a second linear motion transfer means adapted for forceful contact with that second feeler arm having the least radial extension of any said feeler arm and adapted for linear movement corresponding to the extension of said second feeler arm, a second resilient biasing means operative between said first linear transfer means and said second linear transfer means to urge both said first linear transfer means and said second linear transfer means into forceful contact with said first and said second feeler arms, a first rotation responsive sensing means and a second rotation responsive sensing means;

• said first and said second sensing means being respectively connected to said first and said second linear motion transfer means through respective linear/rotary motion transfer means, the combination wherein:
• A. Each of said rotation responsive sensing means is enclosed within an air cavity defined by and isolated from the exterior of said tool;
• and
• B. wherein a rotary shaft is connected between each said sensing means and a respective said linear/rotary motion transfer means through a fluid tight sealing means and a double race end thrust support bearing means.

In an internal diameter caliper having a tool body provided to be coaxially aligned within a generally cylindrical conduit, a plurality of feeler arms with each said feeler arm mounted through bearing means with said body and provided to be urged by respective first resilient biasing means to radially extended positions relative to the axis of said tool, a first linear motion transfer means adapted for forceful contact with that first feeler arm having the greatest radial extension of any said feeler arm and adapted for linear movement corresponding to the extension of said first feeler arm, a second linear motion transfer means adapted for forceful contact with that second feeler arm having the least radial extension of any said feeler arm and adapted for linear movement corresponding to the extension of said second feeler arm, a second resilient biasing means operative between said first linear transfer means and said second linear transfer means to urge both said first linear transfer means and said second linear transfer means into forceful contact with said first and said second feeler arms, and a first rotation responsive sensing means and a second rotation responsive sensing means;

• said first and said second sensing means being respectively connected to said first and said second linear motion transfer means through respective linear/rotary motion transfer means, the combination wherein:
• A. Said bearing means comprises a shaft and V-bearing means adapted to be biased into forceful bearing engagement by said first biasing means to eliminate lost motion between said shaft and said V-bearing.